A cubical block of side `a` and density `rho` slides over a fixed inclined plane with constant velocity `v`. There is a thin film of viscous fluid of thickness `t` between the plane and the block. Then the coefficient of viscosity of the thin film will be: (Acceleration due to gravity is g)

Options

A. `(3rho a g t)/(5v)`
B. `(4rho a g t)/(5v)`
C. `(rho a g t)/(5v)`
D. none of these

Answer

A

Explanation

`mg sin37^(@)=etaA(dv)/(dx)" "rhoa^(3)gxx(3)/(5)=eta a^(2)(v)/(t)" "implies eta=(3rhoag t)/(5v)`